There is a need for quick attach-detach mechanisms which can be utilized not only to enable quick mounting or dismounting of one member to or from another but which also provide for a very secure mounting. This need is particularly pronounced in the aircraft industry wherein it is often desired to mount, inspect and service accessories which weigh in excess of one hundred fifty pounds, such as for example, aircraft engine integrated drive generators. In addition, the space provided around aircraft engines is typically small and relatively inaccessible with the result that it is often difficult to install, service and remove accessories. Thus it is highly desirable that a quick attach-detach mechanism, with a minimum number of assembly steps and parts and which will facilitate installation within this minimal space, be utilized.
Because of the accessory weights typically involved and the limited working area associated with aircraft engines the mounting of engine accessories should ideally be carried out as quickly as possible with a minimum of relative movement, both axially and radially, between the parts being assembled. After mounting, the attach-detach mechanism should perform a positive securing function with no loosening and wear characteristics as a result of engine input and other vibrations.
One prior art approach to providing a quick attach-detach mechanism is disclosed in U.S. Pat. No. 2,645,438, entitled "Mounting Device For Engine Accessories", by I. Kalikow. As disclosed therein, a mounting flange having a plurality of circumferentially extending lugs is secured to an engine casing. The member to be mounted, in this case a dynamoelectric machine, is provided with a circular shoulder and a plurality of lugs projecting from one end of the dynamoelectric machine which form grooves adapted to mate with or fit about wedge shaped lugs projecting from the mounting flange. Assembly is carried out by inserting the end portion of the dynamoelectric machine within the mounting flange. The dynamoelectric machine is then rotated until the two sets of projecting lugs are aligned. Once aligned, the lugs are constricted to wedge tightly within accommodating grooves provided by a clamping means which is tightened around the circumference of the mounting flange.
One of the problems associated with this type of mechanism and assembly procedure is that the dynamoelectric machine must be rotated during the assembly operation. In some aircraft, such machines can weigh in excess of one hundred and fifty pounds. For this reason it is undesirable to utilize a mechanism which would require, not only elevating and aligning of the dynamoelectric or other member with the member to which it is to be joined, but also rotating of the members relative to each other.
Another problem associated with the '438 patent mechanism is the requirement that the wedge-shaped lugs and grooves be machined to provide the desired precision for suitable operation of the mechanism. This machining of such parts can be an expensive and time consuming operation. Moreover, in utilizing a split clamping ring held at opposite sides by threaded screws, yet another problem is introduced. In high vibration environments these screws are subject to loosening, thereby leading to a loosening of the firmly engaged flange lugs. While complex safety devices may well prevent a severe disconnect problem, such systems typically, nevertheless, require frequent monitoring and servicing.
Finally, rotation of the dynamoelectric machine and placement of a ring about the circumference of the mounting flange are operations which can require extra labor and hands and, in the confined spaces often associated with aircraft, can require tedious and time consuming manual operations.
A mechanism utilizing one bolt to mount an accessory on an aircraft engine is depicted in U.S. Pat. No. 2,683,006, entitled "Accessory Mounting Means," by A. D. Nichols. In a first embodiment an engine pad adapter is provided with a circular flange at its inner diameter which is internally threaded with helical splines. An accessory pad adapter is provided with a circular flange at its inner diameter which is externally threaded with helical splines adapted to cooperate with the internal splines of the engine pad adapter. Assembly is effected by rotating the accessory and the accessory pad adapter relative to the engine pad adapter, thereby thread joining the accessory to the engine. Bosses are provided on both adapters, which, because of location, permit insertion of a bolt through both bosses. The members are locked together when a nut is securely threaded on the bolt. This mounting approach suffers from two of the problems enumerated hereinabove. First, in requiring that the accessory be rotated, a very cumbersome and undesirable labor intensive operation is necessitated, particularly when heavy accessories are used. Secondly, severe vibrations can wear and loosen the single bolt and nut locking element, thereby requiring frequent maintenance inspections and tightening operations.
A second embodiment depicted in the '006 patent utilizes torque transmitting splines or lugs on an accessory pad. The splines are adapted to project between torque transmitting splines or lugs on an engine pad adapter. A lock ring which overlaps a portion of the accessory adapter is then threadedly secured to the engine adapter and locked in place by a bolt-nut arrangement. The bolt passes through a boss associated with the engine or engine adapter and another attached to the lock ring. Thus, one bolt prevents the lock ring from loosening. This particular embodiment suffers from the same vibration sensitive wear and loosening problem as discussed hereinabove. Frequent inspection and maintenance operations are required due to the typically high vibration environment associated with aircraft engine operation.
Another approach which is susceptible to vibration induced loosening and wear problems is disclosed in U.S. Pat. No. 2,368,537, entitled "Power Plant Accessory" by S. Gilbert. This patent utilizes a split clamp which overlaps abutting flanges, one of the flanges being attached to a mounting support, the other being part of the accessory. The split clamp overlaps the abutting flanges and is secured thereon by two fasteners, disposed on opposite sides of the clamp. Not only is this type of split clamp subject to frequent loosening via engine and craft vibration but assembly of the clamp elements about the flanges requires a manual assembling operation rendered difficult by space limitations often associated with the area surrounding an aircraft engine.
Yet another variation utilizing a clamp type ring can be found in U.S. Pat. No. 2,439,161 entitled "Attaching Means," by G. B. DuBois. In the '161 patent an engine adapter ring and a portion of the accessory to be mounted are provided with interfitting lugs and fingers. The adapter ring is provided with a plurality of axially extending fingers, each of which is formed with a lug or outwardly directed flange at its free end. The outer surface of the accessory is provided with a plurality of circumferentially spaced lugs adapted to be received between the fingers of the adapter ring. Adjacent sides of the adapter ring and accessory lugs are spaced apart and machined or beveled to receive an inwardly beveled clamp ring, which when tightened by a bolt, causes a wedging action between the beveled sides assembling the members together. Again, as discussed hereinabove, intense vibration frequently encountered within aircraft environments tends to cause wear and loosening problems requiring frequent inspection and maintenance procedures. In addition, utilization of machined and beveled surfaces requires expensive machining operations in manufacturing the mounting assemblies.
Several other variations of prior art devices utilizing clamp type rings for securing two members together are depicted in U.S. Pat. No. 2,544,151 to S. Gilbert et al, entitled "Element And Accessory of Power Plants;" U.S. Pat. No. 2,553,220 to H. Troeger, entitled "Quick Detachable Means;" U.S. Pat. No. 2,697,570 to J. R. Snyder, entitled "Quick-Attaching Device;" and U.S. Pat. No. 2,978,265 to H. E. Cluff et al, entitled "Quick Disconnect Coupling." All of these patents disclose a clamp-type ring for securing flange structures together via activation of a single fastening device attached to the ends of the clamping ring. These devices are subject to many of the same wear, loosening, inspection and maintenance problems discussed hereinabove.
Also known in the prior art are interconnect systems which work through the utilization of slotted interconnect of the two members being assembled. That is, one of the members to be assembled is provided with protruding bolts circumferentially spaced and carrying nuts on the ends thereof. The other member is provided with a plurality of key slots circumferentially spaced such that the protruding bolts carrying the nuts can be passed through the large end of corresponding key slots. The two members are then rotated relative to each other such that the bolts move circumferentially to the narrow end of the slots. The individual nuts can then be tightened against the surface adjacent the narrow portion of the slots, thereby securing the two members together. This particular type of interconnect system is difficult in an environment where rotation of either or both of the members is difficult, or where there are severe limitations as to working area available, as is often the situation when mounting heavy accessories to aircraft engines.
In view of the problems associated with the aforementioned prior art devices, there is a need for an improved attach-detach mechanism and process for the securing of one member to another. Ideally the mechanism and process should provide for a good, positive, multiple fastener connection between members which will resist vibration and harsh environment wear and loosening problems. Such a connection should simultaneously be adapted to be quickly accomplished with a minimum of labor and with little or no relative rotation of the members, so as to be utilizable in a severely limited working area, as, for example, areas typically found in and around aircraft engines.
From the foregoing, it can be seen that it is a primary object of this invention to provide a quick attach-detach mechanism for attaching one member to another whereby securement of the members together is positive and highly resistant to wear and loosening effects as a result of vibrations encountered during use.
It is also an object of this invention to provide a quick attach-detach mechanism which can be utilized in a space restricted work area, and which can be utilized to accomplish securing of two members to each other in such a restricted area without appreciable rotation of either member relative to the other.
A further object of this invention is to provide a quick attach-detach mechanism for mounting an engine accessory such as a dynamoelectric machine to the accessory gearbox of an aircraft engine whereby the mechanism is resistent to severe wear and loosening effects of engine vibration.
A still further object of this invention is to provide an accessory attach-detach mechanism which utilizes several securement elements, operates as a quick assembly and disassembly mechanism in a limited working area, functions without the need to rotate either the accessory or the member to which the accessory is to be mounted, and is simple to manufacture, requiring few, if any, complex and expensive machining operations.